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          <h1 class="post-title" itemprop="name headline">C++之运算符重载详解</h1>
        

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        <p>C++允许对同一作用域中的某个函数和运算符指定多个定义，分别为函数重载和运算符重载，这里主要说明运算符重载在C++中的使用。</p>
<a id="more"></a>
<hr>
<h1 id="重载运算符"><a href="#重载运算符" class="headerlink" title="重载运算符"></a>重载运算符</h1><p>在C++中可以重载的运算符如下：</p>
<table>
<thead>
<tr>
<th>名称</th>
<th>运算符</th>
</tr>
</thead>
<tbody>
<tr>
<td>双目算数运算符</td>
<td>+、-、*、/</td>
</tr>
<tr>
<td>关系运算符</td>
<td>==、!=、&lt;、&gt;、&lt;=、&gt;=</td>
</tr>
<tr>
<td>逻辑运算符</td>
<td>与、或、非</td>
</tr>
<tr>
<td>单目运算符</td>
<td>+ (正)，-(负)，*(指针)，&amp;(取地址)</td>
</tr>
<tr>
<td>自增自减运算符</td>
<td>++、-</td>
</tr>
<tr>
<td>位运算符</td>
<td>(按位或)，&amp; (按位与)，~(按位取反)，^(按位异或),，&lt;&lt; (左移)，&gt;&gt;(右移)</td>
</tr>
<tr>
<td>赋值运算符</td>
<td>=, +=, -=, *=, /= , % = , &amp;=,</td>
</tr>
<tr>
<td>空间申请与释放</td>
<td>new、delete、new[]、delete[]</td>
</tr>
<tr>
<td>其他运算符</td>
<td>()（函数调用）、-&gt;（成员访问）、,（逗号）、[]）（下标）</td>
</tr>
</tbody>
</table>
<p>不可重载运算符：</p>
<p>​    1.：成员访问运算符</p>
<p>​    2<em> 、 -&gt;</em>：成员指针访问运算符</p>
<p>​    3.：：域运算符</p>
<p>​    4.sizeof:长度运算符</p>
<p>​    5.?::条件运算符</p>
<p>​    6.#：预处理符号</p>
<p>一些限制：</p>
<p>​    1.无法重载所有操作数均为基本类型的操作符</p>
<p>​    2.无法通过重载操作符改变操作符的优先级</p>
<p>​    3.无法通过操作符改变操作数的个数</p>
<p>​    4.无法通过操作符重载发明新的操作符</p>
<p>​    5.操作符重载着力堆一致性的追求</p>
<hr>
<h1 id="重载函数"><a href="#重载函数" class="headerlink" title="重载函数"></a>重载函数</h1><p>运算符重载函数一般有两种形式：重载为<strong>类的成员函数</strong>和重载为<strong>类的非成员函数</strong>。非成员函数通常是友元。（可以把一个运算符作为一个非成员、非友元函数重载。但是，这样的运算符函数访问类的私有和保护成员时，必须使用类的公有接口中提供的设置数据和读取数据的函数，调用这些函数时会降低性能。可以内联这些函数以提高性能。）</p>
<p>运算符重载为类的成员函数的一般格式：</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">&lt;函数类型&gt; operator &lt;运算符&gt; (&lt;参数表&gt;)</span><br><span class="line">&#123;</span><br><span class="line">    &lt;函数体&gt;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<p>调用成员函数运算符格式如下：</p>
<p>&lt;对象名&gt;.operator &lt;运算符&gt; (&lt;参数&gt;)</p>
<p>等价于：</p>
<p>&lt;对象名&gt;&lt;运算符&gt;&lt;参数&gt;</p>
<p>例如：a+b =&gt; a.operator +(b)</p>
<p>运算符重载为类的友元函数的一般格式为：</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">friend &lt;函数类型&gt; operator &lt;运算符&gt; (&lt;参数表&gt;)</span><br><span class="line">&#123;</span><br><span class="line">    &lt;函数体&gt;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<p>调用友元函数运算符格式如下：</p>
<p>operator &lt;运算符&gt; (&lt;参数1&gt;，&lt;参数2&gt;)</p>
<p>等价于：</p>
<p>&lt;参数1&gt;&lt;运算符&gt;&lt;参数2&gt;</p>
<p>&lt;参数1&gt;&lt;运算符&gt;&lt;参数2&gt;</p>
<hr>
<h1 id="运算符重载实例"><a href="#运算符重载实例" class="headerlink" title="运算符重载实例"></a>运算符重载实例</h1><p>上面介绍了一些基本概念，对于运算符重载还是有很多坑，尤其是运算符重载结合指针使用的时候，很容易会出现内容泄露的问题。<br>eg1：创建一个复数类，实现+，-，+=， -=，-，~，&lt;&lt;，&gt;&gt;</p>
<figure class="highlight c++"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br><span class="line">89</span><br><span class="line">90</span><br><span class="line">91</span><br><span class="line">92</span><br><span class="line">93</span><br><span class="line">94</span><br><span class="line">95</span><br><span class="line">96</span><br><span class="line">97</span><br><span class="line">98</span><br><span class="line">99</span><br><span class="line">100</span><br><span class="line">101</span><br><span class="line">102</span><br><span class="line">103</span><br><span class="line">104</span><br><span class="line">105</span><br><span class="line">106</span><br><span class="line">107</span><br><span class="line">108</span><br><span class="line">109</span><br><span class="line">110</span><br><span class="line">111</span><br><span class="line">112</span><br><span class="line">113</span><br><span class="line">114</span><br><span class="line">115</span><br><span class="line">116</span><br><span class="line">117</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="meta-keyword">include</span> <span class="meta-string">&lt;iostream&gt;</span></span></span><br><span class="line"><span class="keyword">using</span> <span class="keyword">namespace</span> <span class="built_in">std</span>;</span><br><span class="line"></span><br><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Complex</span></span></span><br><span class="line"><span class="class">&#123;</span></span><br><span class="line"><span class="keyword">public</span>:</span><br><span class="line">    Complex(<span class="keyword">int</span> i = <span class="number">0</span>, <span class="keyword">int</span> j = <span class="number">0</span>) : m_i(i), m_j(j) &#123;&#125;</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">void</span> <span class="title">print</span><span class="params">()</span> <span class="keyword">const</span></span></span><br><span class="line"><span class="function">    </span>&#123;</span><br><span class="line">        <span class="built_in">cout</span> &lt;&lt; m_i &lt;&lt; <span class="string">'+'</span> &lt;&lt; m_j &lt;&lt; <span class="string">"i"</span> &lt;&lt; <span class="built_in">endl</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">const</span> Complex <span class="keyword">operator</span>+(<span class="keyword">const</span> Complex &amp;r) <span class="keyword">const</span></span><br><span class="line">    &#123;</span><br><span class="line">        <span class="keyword">return</span> Complex(m_i + r.m_i, m_j + r.m_j);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    Complex &amp;<span class="keyword">operator</span>+=(<span class="keyword">const</span> Complex &amp;r)</span><br><span class="line">    &#123;</span><br><span class="line">        m_i += r.m_i;</span><br><span class="line">        m_j += r.m_j;</span><br><span class="line">        <span class="keyword">return</span> *<span class="keyword">this</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">const</span> Complex <span class="keyword">operator</span>-() <span class="keyword">const</span></span><br><span class="line">    &#123;</span><br><span class="line">        <span class="keyword">return</span> Complex(-m_i, -m_j);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">const</span> Complex <span class="keyword">operator</span>~() <span class="keyword">const</span></span><br><span class="line">    &#123;</span><br><span class="line">        <span class="keyword">return</span> Complex(m_j, m_i);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    Complex &amp;<span class="keyword">operator</span>++()</span><br><span class="line">    &#123;</span><br><span class="line">        ++m_i;</span><br><span class="line">        ++m_j;</span><br><span class="line">        <span class="keyword">return</span> *<span class="keyword">this</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">operator</span> <span class="title">int</span><span class="params">()</span> <span class="keyword">const</span></span></span><br><span class="line"><span class="function">    </span>&#123;</span><br><span class="line">        <span class="keyword">return</span> m_i;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">const</span> Complex <span class="keyword">operator</span>++(<span class="keyword">int</span>)</span><br><span class="line">    &#123;</span><br><span class="line">        <span class="function">Complex <span class="title">old</span><span class="params">(*<span class="keyword">this</span>)</span></span>;</span><br><span class="line">        ++m_i;</span><br><span class="line">        ++m_j;</span><br><span class="line">        <span class="keyword">return</span> old;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">friend</span> <span class="keyword">const</span> Complex <span class="keyword">operator</span>-(<span class="keyword">const</span> Complex &amp;l, <span class="keyword">const</span> Complex &amp;r)</span><br><span class="line">    &#123;</span><br><span class="line">        <span class="keyword">return</span> Complex(l.m_i - r.m_i, l.m_j - r.m_j);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">friend</span> Complex &amp;<span class="keyword">operator</span>--(Complex &amp;l)</span><br><span class="line">    &#123;</span><br><span class="line">        --l.m_i;</span><br><span class="line">        --l.m_j;</span><br><span class="line">        <span class="keyword">return</span> l;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">friend</span> Complex &amp;<span class="keyword">operator</span>-=(Complex &amp;l, <span class="keyword">const</span> Complex &amp;r)</span><br><span class="line">    &#123;</span><br><span class="line">        l.m_i -= r.m_i;</span><br><span class="line">        l.m_j -= r.m_j;</span><br><span class="line">        <span class="keyword">return</span> l;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">friend</span> ostream &amp;<span class="keyword">operator</span>&lt;&lt;(ostream &amp;os, <span class="keyword">const</span> Complex &amp;r)</span><br><span class="line">    &#123;</span><br><span class="line">        <span class="keyword">return</span> os &lt;&lt; r.m_i &lt;&lt; <span class="string">'+'</span> &lt;&lt; r.m_j &lt;&lt; <span class="string">'i'</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">friend</span> istream &amp;<span class="keyword">operator</span>&gt;&gt;(istream &amp;is, Complex &amp;r)</span><br><span class="line">    &#123;</span><br><span class="line">        <span class="keyword">return</span> is &gt;&gt; r.m_i &gt;&gt; r.m_j;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span>:</span><br><span class="line">    <span class="keyword">int</span> m_i;</span><br><span class="line">    <span class="keyword">int</span> m_j;</span><br><span class="line">&#125;;</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">int</span> <span class="title">main</span><span class="params">()</span></span></span><br><span class="line"><span class="function"></span>&#123;</span><br><span class="line">    Complex c1(1, 2), c2(2, 3);</span><br><span class="line">    <span class="built_in">cout</span> &lt;&lt; c1 + c2 &lt;&lt; <span class="built_in">endl</span>;</span><br><span class="line">    <span class="built_in">cout</span> &lt;&lt; c1 - c2 &lt;&lt; <span class="built_in">endl</span>;</span><br><span class="line">    c1 += c2;</span><br><span class="line">    c1.print();</span><br><span class="line">    c1 -= c2;</span><br><span class="line">    c1.print();</span><br><span class="line">    <span class="function">Complex <span class="title">c3</span><span class="params">(<span class="number">5</span>, <span class="number">6</span>)</span></span>;</span><br><span class="line">    (c1 += c2) = c3;</span><br><span class="line">    c1.print();</span><br><span class="line"></span><br><span class="line">    <span class="built_in">cout</span> &lt;&lt; c1 &lt;&lt; <span class="built_in">endl</span></span><br><span class="line">         &lt;&lt; c2 &lt;&lt; <span class="built_in">endl</span>;</span><br><span class="line">    <span class="comment">// cin &gt;&gt; c1 &gt;&gt; c2;</span></span><br><span class="line">    <span class="comment">// cout &lt;&lt; c1 &lt;&lt; endl &lt;&lt; c2;</span></span><br><span class="line"></span><br><span class="line">    <span class="built_in">cout</span> &lt;&lt; -c1 &lt;&lt; <span class="built_in">endl</span>;</span><br><span class="line">    <span class="built_in">cout</span> &lt;&lt; ~c1 &lt;&lt; <span class="built_in">endl</span>;</span><br><span class="line"></span><br><span class="line">    <span class="built_in">cout</span> &lt;&lt; --c1 &lt;&lt; <span class="built_in">endl</span>;</span><br><span class="line">    <span class="built_in">cout</span> &lt;&lt; ++c1 &lt;&lt; <span class="built_in">endl</span>;</span><br><span class="line">    <span class="built_in">cout</span> &lt;&lt; c1++ &lt;&lt; <span class="built_in">endl</span>;</span><br><span class="line">    <span class="built_in">cout</span> &lt;&lt; <span class="keyword">int</span>(c1) &lt;&lt; <span class="built_in">endl</span>;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<p>运行结果：</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line">-1+-1i</span><br><span class="line">3+5i</span><br><span class="line">1+2i</span><br><span class="line">5+6i</span><br><span class="line">5+6i</span><br><span class="line">2+3i</span><br><span class="line">-5+-6i</span><br><span class="line">6+5i</span><br><span class="line">4+5i</span><br><span class="line">5+6i</span><br><span class="line">5+6i</span><br><span class="line">6</span><br></pre></td></tr></table></figure>
<p>eg2:实现一个String类，支持=</p>
<figure class="highlight c++"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">String</span></span></span><br><span class="line"><span class="class">&#123;</span></span><br><span class="line"><span class="keyword">public</span>:</span><br><span class="line">    String(<span class="keyword">const</span> <span class="keyword">char</span> *str = <span class="literal">NULL</span>)</span><br><span class="line">    &#123;</span><br><span class="line">        m_str = <span class="keyword">new</span> <span class="keyword">char</span>[<span class="built_in">strlen</span>(str ? str : <span class="string">""</span>) + <span class="number">1</span>];</span><br><span class="line">        <span class="built_in">strcpy</span>(m_str, str ? str : <span class="string">""</span>);</span><br><span class="line">    &#125;</span><br><span class="line">    ~String()</span><br><span class="line">    &#123;</span><br><span class="line">        <span class="keyword">if</span> (m_str)</span><br><span class="line">        &#123;</span><br><span class="line">            <span class="keyword">delete</span>[] m_str;</span><br><span class="line">            m_str = <span class="literal">NULL</span>;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    String(<span class="keyword">const</span> String &amp;that) : m_str(<span class="built_in">strcpy</span>(<span class="keyword">new</span> <span class="keyword">char</span>[<span class="built_in">strlen</span>(that.m_str) + <span class="number">1</span>], that.m_str)) &#123;&#125;</span><br><span class="line"></span><br><span class="line">    String &amp;<span class="keyword">operator</span>=(<span class="keyword">const</span> String &amp;that)</span><br><span class="line">    &#123;</span><br><span class="line">        <span class="keyword">if</span> (&amp;that != <span class="keyword">this</span>)</span><br><span class="line">        &#123;</span><br><span class="line">            String temp(that);</span><br><span class="line">            swap(m_str, temp.m_str);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">const</span> <span class="keyword">char</span> *<span class="title">c_str</span><span class="params">()</span> <span class="keyword">const</span></span></span><br><span class="line"><span class="function">    </span>&#123;</span><br><span class="line">        <span class="keyword">return</span> m_str;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">operator</span> <span class="keyword">const</span> <span class="keyword">char</span> *() <span class="keyword">const</span></span><br><span class="line">    &#123;</span><br><span class="line">        <span class="keyword">return</span> c_str();</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span>:</span><br><span class="line">    <span class="keyword">char</span> *m_str;</span><br><span class="line">&#125;;</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">int</span> <span class="title">main</span><span class="params">()</span></span></span><br><span class="line"><span class="function"></span>&#123;</span><br><span class="line">    <span class="function">String <span class="title">str</span><span class="params">(<span class="string">"Hello World"</span>)</span></span>;</span><br><span class="line">    <span class="built_in">cout</span> &lt;&lt; str.c_str() &lt;&lt; <span class="built_in">endl</span>;</span><br><span class="line">    <span class="function">String <span class="title">s2</span><span class="params">(<span class="string">"Hello Luqilin"</span>)</span></span>;</span><br><span class="line">    str = s2;</span><br><span class="line">    <span class="built_in">cout</span> &lt;&lt; str.c_str() &lt;&lt; <span class="built_in">endl</span>;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<p>运行结果：</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">Hello World</span><br><span class="line">Hello Luqilin</span><br></pre></td></tr></table></figure>

      
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              <div class="post-toc-content"><ol class="nav"><li class="nav-item nav-level-1"><a class="nav-link" href="#重载运算符"><span class="nav-number">1.</span> <span class="nav-text">重载运算符</span></a></li><li class="nav-item nav-level-1"><a class="nav-link" href="#重载函数"><span class="nav-number">2.</span> <span class="nav-text">重载函数</span></a></li><li class="nav-item nav-level-1"><a class="nav-link" href="#运算符重载实例"><span class="nav-number">3.</span> <span class="nav-text">运算符重载实例</span></a></li></ol></div>
            

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